Prior art of possible relevance includes the following U.S. Pat. Nos. 3,689,786 issued Sept. 5, 1972 and 4,119,872 issued Oct. 10, 1978, both to Hunt.
As is well known, the capacity of a dynamoelectric machine can be increased substantially if heat generated during its operation can be rejected from the machine itself. Consequently, most dynamoelectric machines today include some provision for flowing a fluid coolant across some part of the machine structure. Care must be taken, however, to prevent the coolant from causing undesirable windage losses. Windage is the energy loss due to shear forces acting within fluids disposed between relatively moving parts of the machine as, for example, in the so-called air gap between the rotor and the stator. Windage losses are affected by a variety of factors including the relative speed between two relatively moving components, the distance and area over which shear takes place, and the geometrical configuration of various components. The air gap between the stator and the rotor is the most significant concern as a source of windage losses and losses of an extremely high magnitude have been observed for high speed machines when a liquid coolant migrates to the air gap.
As a consequence, there have been a number of proposals for preventing coolant from entering the air gap including some wherein the coolant is always housed within conduits, which may even comprise the conductors themselves, in the rotor and stator and which form part of a coolant flow path which is completely isolated from the air gap. While systems of this sort work well in preventing undue windage losses, they are extremely expensive and accordingly are not cost effective for all applications.
As a cost effective means for providing cooling of a dynamoelectric machine, direct contact cooling with a liquid coolant is preferred. The above identified Hunt patents show the use of weirs in connection with direct contact cooling, principally of rotor components. However, care must be taken to keep deflected and splashed liquid away from and out of the air gap, or else undesirably high windage losses may come into existence, and the Hunt patents fail to deal with this problem.
Thus, the invention is directed to providing a low cost, cost efficient, direct contact cooling structure for use in dynamoelectric machines, which is such as to be highly efficient in preventing entry of liquid coolant into the air gap between the rotor and the stator of such machines, to thereby minimize windage losses.